You should be getting events in NTA saying that you are receiving flows from IP address that belongs to the vSphere switch> click manage link in that event > add as ICMP or External node > then check NTA again after minute or two, and there should be another event saying you are receiving flows from interface #xx, with link to add interface > follow the link, it should create a 'Virtual Interface xx' (specify the speed on interface) > if you have automatic netflow source addition enabled you should automatically start receiving flows from the switch.

Unfortunately it has to be added one by one currently :-( I understand that it is painful...